Nakamichi BX-300 (The Second One)

[laatsch55]

Darc, Joe says a direct drop in with much better performance!!

 

[laatsch55]

The OPA 2134....

 

[derek92994]

Darc, Joe says a direct drop in with much better performance!!

Ok OPA2134 it is. Thanks so much Lee.

I'm looking at taking it even further by following exact calibration steps from the service manual. Previously I have only done Wow/Flutter, and speed adjust using a scope program on my computer and a test tape which was made by a professional. The service manual mentions a Vacuum Tube Volt-Ohm Meter which is used for the majority of the tests. It seems that there are only vintage units of these still available 2nd hand. My question is, what alternatives do I have? Is there something more modern that I can use or purchase fairly cheaply?

 

[derek92994]

Also a Big Thanks to Joe for the advice on the OP Amp, us Amateurs need all the help we can get! I hope in time that I can get up to Pro level with these decks when it comes to service manual calibrations.

 

[derek92994]

Ok upon searching the internet, they say I can use a multi meter. I will take a screenshot from the service manual and a picture of the multi meter.

What setting and input do I use on this thing?

 

[laatsch55]

AC millivolts....

 

[derek92994]

Dropped the OP2134PA into Line input stage, it worked and sounds great. Recorded Natalie Merchant's 'Tigerlily' MFSL CD, excellent result. I will also upgrade the other two decks with this mod including muse caps.

 

[derek92994]

AC millivolts....

Thanks Lee, AC? Really? well, I guess you learn something every day!

 

[derek92994]

Why AC? isn't everything DC after the power supply section?

 

[laatsch55]

You are measuring recorded music......but i'm not familiar enough with the biasing of a tape to know if it's a pure ac signal. Come to think of it....I don't have a clue...try AC volts first...

 

[derek92994]

You are measuring recorded music......but i'm not familiar enough with the biasing of a tape to know if it's a pure ac signal. Come to think of it....I don't have a clue...try AC volts first...

Measuring tones inputted to ensure output measures a certain level to match factory calibration standards. Will look at bias later. Thanks bud.

 

[mlucitt]

Love those Burr Browns... Somebody at Texas Instruments was a smart guy. Putting an FET as the front end of an OP Amp, there's an idea!

 

[derek92994]

Love those Burr Browns... Somebody at Texas Instruments was a smart guy. Putting an FET as the front end of an OP Amp, there's an idea!

Burr Browns are great, and they are Cheap! $8 Australian, that is retail though, not online price.
I Still have to complete the OP Amps in BX-300 the 1st, that will be done today.

 

[ksrigg]

What is the best player to buy with potential? Given a 500 dollar budget what would you buy and what needs to be done to make it GREAT???

 

[orange]

I already own a Pioneer CT-F1250 that I bought from a Tapeheads member for $465 and had very little use when I got it.

 

[derek92994]

What is the best player to buy with potential? Given a 500 dollar budget what would you buy and what needs to be done to make it GREAT???

I would recommend a Bx-300 fully restored with the caps in the psu and audio path replaced (audio grade caps)

 

[orange]

I got a $2 Akal HX-2 from 1981 at a local auction that is just flat out amazing as well. A real workhorse. The controls are a little different but when you get used to them it's simple. !980s Akai gear is pretty darn cool anyway and I've had tuners and integrateds in ther house plus the EA-A7 Computer Graphic Equalizer with the HX-2. Got the EQ from Doity on TH.

 

[derek92994]

Lee, thanks for the advice on using AC Milivolts, I managed to fully recap and calibrate this unit

I had a faulty replacement 100v/0.018uf Cap which was giving me hell on the Bias board. Ended up using the original Orange cap until I figured this out, Yep new caps can be faulty from the factory.

My OCD kicked in and I just had to upgrade the Power supply caps. Maybe its the colour?

 

[laatsch55]

You've been a busy guy Darc!!

 

[derek92994]

You've been a busy guy Darc!!

Yeah its been fun, keeps the mind occupied. Best part is listening.